1. Field of the Invention
The present invention pertains to pacemakers or defibrillators, and more particularly, pertains to remote programming of a pacemaker or defibrillator by the use of a radio frequency repeater device placed in close proximity to the implanted stimulation device.
2. Description of the Prior Art
Prior art implanted devices, such as pacemakers or defibrillators, are normally packaged in titanium cases. The metallic case provides hermiticity and serves as a shield for stray electrical fields which may interfere with operation of the device's electronics. The shield also has the effect of attenuating the RF signals from a programming device, which are necessary to configure the electronics for a given patient. Because of the shielding effects of the metal case, and of the patient's own body, it is usually necessary to place the programming antenna as close to the implanted device as the exterior of the patient's body permits.
The programming device is usually a large non-sterilizable box with an antenna connected to it with a coiled umbilical cord. In surgery, the antenna wand is usually covered with a long sterile plastic bag. The physician then handles the wand in the sterile field. The limited space usually requires the physician to hold the wand and give verbal instructions to a nurse who is operating the programmer at a spaced distance. The springiness of the coiled cord make setting the wand down risky, and the distance from the physician to the programmer usually precludes his seeing the programmer display. The whole situation is unwieldy. Sometimes the coiled cord caused the wand to repel and even fall on the floor of the operating room, requiring recovering the wand with a new sterile plastic bag.
The present invention overcomes the deficiencies of the prior art by providing a small sterilizable battery-operated repeater unencumbered by connecting cords or wires which repeats informational data code to the pacemaker or defibrillator via RF transmissions from a remotely placed programmer.
Shortcomings of the prior art methods can be summarized by noting that they place incompatible, essentially contradictory requirements on both apparatus and human participants in the programming procedure. The element that transmits and receives RF signals to and from the implanted stimulator must be sterilizable. While it is outside the patient's body, it is well within the sterile zone or field that must be maintained in and near the patient in an operating room. Further requirements are that it must be accurately positionable and easily maintained in that position. For effective use it should also be comparatively small.
The programming unit, on the other hand, is inherently nonsterilizable, because it incorporates electromechanical input components (pushbuttons, switches, dials) and electromechanical and electronic readout devices (gauges, meters, digital displays), and these do not lend themselves to sterilizable design. Furthermore, the programming unit can be more easily and accurately used if it is permitted to grow to a comfortably large size, affording room for finger-sized pushbuttons and easily read displays. These incompatibilities are bridged in the prior art by means of an interconnecting cable, coiled for flexibility, but still heavy enough and stiff enough to disturb the position of the antenna element.
The contradictory human requirements arise because the attending surgeon must address two functions simultaneously: There is the mechanical task of maintaining the antenna component in the right position in the presence of the forces on it exerted by the cable, and the intellectual task of articulating instructions to an assistant, this without benefit of visual feedback from observing the displays as his or her instructions are executed by the assistant, or the motor feedback that would be derived if he or she were personally executing the programming. It will be seen that the present invention eliminates self-contradictory requirements from both the human participant and the apparatus.